Yu-Gi-Oh! TCG

The Official Card Game (OCG) is the Asian version of the Yu-Gi-Oh card game, which is primarily played in Japan and China. The Trading Card Game (TCG) is the version of the game that exists for Western territories like Europe and North America. While both games are very similar, there are a number of key differences which are mostly around the banlists of the respective games.
The differences in the ban lists are significant enough that the OCG and TCG are considered separate from each other, with high level competitive tournaments run separately for eastern and western territories.
OCG cards cannot be used in the TCG and vice versa.

The Yu-Gi-Oh! TCG ban list is fluid and will change in response to new decks, as it attempts to make the game more fair and balanced. You can find the Yu-Gi-Oh! TCG banlist on the official Yu-Gi-Oh website.

Yes, many can be worth a lot! The price of newer cards tends to be driven by the popularity of the card in competitive play, or in other words, cards played frequently in the competitive meta. Older cards do not see frequent play in the competitive scene but can be valuable as collectible items. Still have that first edition Blue Eyes White Dragon, Dark Magician, or Exodia pieces sitting around in a binder? There’s a good chance they would be quite valuable.

The rarity of Yu-Gi-Oh cards is signified by the foiling on the card. Generally speaking, if it has any foil on the card, it would be considered rare. Here are some examples of Yu-Gi-Oh card rarities: 

-‘Common’ cards have no foiling. ‘Rare’ cards have foiling only on the name of the card.
-‘Super Rare’ cards have foiling over the artwork of the card only
-‘Ultra Rare’ cards have foiling over the name of the card and artwork.

Beyond this, there are many other foiling styles used for other rare cards. Here are some of the most recent types:

-’Ultimate Rare’ cards are special embossed foil cards and can most easily be recognised by the embossed foil over the levels of the cards and the texturing over the artwork of the card
-’Secret Rare’ cards have a special holographic foiling over the artwork of the card
-’Starlight Rare’ cards are like ‘Secret Rare cards but have the holographic foiling over the whole card
-’Quarter Century Secret Rare’ cards are similar to Starlight rare cards and have a holographic foiling over the whole card, as well as a 25th Anniversary emblem over the text on the card.

A first edition Yu-Gi-Oh card is a card that was printed in the first print run of a particular set or structure deck. If the set or structure deck is reprinted, it is printed as the ‘Unlimited’ version. 

First edition cards can be recognised by looking along the bottom of the card, where it would show ‘1st Edition’. The holographic seal in the bottom right corner of the card would also be gold. The ‘Unlimited’ counterpart would be silver.

The first edition cards are generally considered more desirable, and hence carry a higher price tag compared to the equivalent ‘Unlimited’ card.